This invention relates to the manufacture of shaped parts or structures from fabrics having good resistance to high temperatures and good tensile strength characteristics. These shaped parts are usually then impregnated with resin and cured. The parts have use in aerospace where lightweight structures with good tensile properties are important.
In the prior art, lightweight shaped structures of multi-ply woven fabric are initially formed by wrapping or conforming individually pre-cut strips of the fabric around a shaped structure that is usually a mold. The structure may have a shape such as a box, hemisphere, an ojive, a five or eight sided container, etc. The wrapped parts are then impregnated with a thermosetting resin and then cured. The technique of using pre-cut and pre-shaped strips of fabric is necessary, because many parts have sharp edges and corners that defy a uniform wrapping using individual, wide fabric plies. It would be preferred to employ a continuous fabric that is wrapped around a mold to form these type of parts, rather than applying discontinuous strips to a mold surface. However, it has been found that while the inner ply of the usual three-ply fabric will conform to the structure, the outer ply of the fabric becomes excessively stretched, particularly around corners, edges, crevices, etc.
In addition, these prior art techniques of wrapping individually shaped strips of fabric around a structure require that the wrapped shapes are impregnated with resin very soon after they are produced. In many cases this necessitates that the prepeg material be kept on hand and refrigerated.
Obviously, it would be preferred to wrap a multi-ply fabric around a structure that can accommodate for variations of its non uniform surface.
Also, it would be preferred to eliminate the need for applying pre-cut and pre-shaped strips to a structure, and instead to form the lightweight shape in a single wrapping operation; this would reduce production costs.